Electrochemistry

Consider the following electrochemical cell at standard condition. Au(s) | QH2, Q | NH4X(0.01 M) || Ag+(1 M) | Ag(s) Ecell = +0.4 V The couple QH2/Q represents quinhydrone electrode, the half cell reaction is given below: [figure] [Given : E0 Ag+/Ag = +0.8 V and 2.303RTF = 0.06 V] The pKb value of the ammonium halide salt (NH4X) used here is . (nearest integer)

0.2\% (w/v) solution of NaOH is measured to have resistivity 870.0 m m. The molar conductivity of the solution will be 102 mS dm2 mol-1. (Nearest integer)

For a Mg | Mg2+(aq) || Ag+(aq) | Ag the correct Nernst Equation is :

1. Ecell = E cell - RT2F [Ag+]2[Mg2+]
2. Ecell = E cell - RT2F [Mg2+][Ag+]
3. Ecell = E cell - RT2F [Ag+][Mg2+]
4. Ecell = E cell + RT2F [Ag+]2[Mg2+]

The molar conductivity of a weak electrolyte when plotted against the square root of its concentration, which of the following is expected to be observed?

1. Molar conductivity increases sharply with increase in concentration.
2. Molar conductivity decreases sharply with increase in concentration.
3. A small increase in molar conductivity is observed at infinite dilution.
4. A small decrease in molar conductivity is observed at infinite dilution.

Match List - I with List - II : Choose the correct answer from the options given below :

1. (A)-(III), (B)-(I), (C)-(IV), (D)-(II)
2. (A)-(II), (B)-(III), (C)-(IV), (D)-(I)
3. (A)-(IV), (B)-(III), (C)-(II), (D)-(I)
4. (A)-(III), (B)-(II), (C)-(IV), (D)-(I)

O2 gas will be evolved as a product of electrolysis of : Choose the correct answer from the options given below :

1. (B) and (C) only
2. (B) and (D) only
3. (A) and (D) only
4. (A) and (C) only

Given below is the plot of the molar conductivity vs concentration for KCl in aqueous solution. [figure] If, for the higher concentration of KCl solution, the resistance of the conductivity cell is 100 , then the resistance of the same cell with the dilute solution is 'x' . The value of x is (Nearest integer)

Electrolysis of 600 mL aqueous solution of NaCl for 5 min changes the pH of the solution to 12. The current in Amperes used for the given electrolysis is . (Nearest integer).

For the given cell Fe2+(aq) + Ag+(aq) Fe3+(aq) + Ag(s) The standard cell potential of the above reaction is Given: Ag+ + e- Ag E = xV Fe2+ + 2e- Fe E = yV Fe3+ + 3e- Fe E = zV

1. x + 2y - 3z
2. x + 2y
3. y - 2x
4. x + y - z

Based on the data given below : E (Cr2O72-/Cr3+)=1.33 V E (Cl2/Cl-)=1.36 V E (MnO4-/Mn2+)=1.51 V E (Cr3+/Cr)=-0.74 V the strongest reducing agent is :

1. Cl-
2. MnO4-
3. Cr
4. Mn2+

FeO42- +2.0 V Fe3+ 0.8 V Fe2+ -0.5 V Fe0 In the above diagram, the standard electrode potentials are given in volts (over the arrow). The value of E (FeO42-/Fe2+) is :

1. 1.2 V
2. 2.1 V
3. 1.4 V
4. 1.7 V

Standard electrode potentials for a few half cells are mentioned below : E Cu2+/Cu = 0.34 V, E Zn2+/Zn = -0.76 V E Ag+/Ag = 0.80 V, E Mg2+/Mg = -2.37 V Which one of the following cells gives the most negative value of G ?

1. Zn | Zn2+(1M) || Ag+(1M) | Ag
2. Ag | Ag+(1M) || Mg2+(1M) | Mg
3. Zn | Zn2+(1M) || Mg2+(1M) | Mg
4. Cu | Cu2+(1M) || Ag+(1M) | Ag

Which of the following electrolyte can be used to obtain H2S2O8 by the process of electrolysis ?

1. Concentrated solution of sulphuric acid
2. Dilute solution of sodium sulphate.
3. Acidified dilute solution of sodium sulphate.
4. Dilute solution of sulphuric acid

A solution of aluminium chloride is electrolysed for 30 minutes using a current of 2 A. The amount of the aluminium deposited at the cathode is . [Given : molar mass of aluminium and chlorine are 27 g mol-1 and 35.5 g mol-1 respectively. Faraday constant = 96500 C mol-1]

1. 1.660 g
2. 1.007 g
3. 0.336 g
4. 0.441 g

Given below are two statements : In the light of the above statements, choose the correct answer from the options given below :

1. Both Statement I and Statement II are true
2. Both Statement I and Statement II are false
3. Statement I is true but Statement II is false
4. Statement I is false but Statement II is true

The molar conductivity for electrolytes A and B are plotted against C1/2 as shown below. Electrolytes A and B respectively are: [figure]

1. A - weak electrolyte B - weak electrolyte
2. A - weak electrolyte B - strong electrolyte
3. A - strong electrolyte B - strong electrolyte
4. A - strong electrolyte B - weak electrolyte

The standard reduction potentials at 298 K for the following half cells are given below : Cr2O72- + 14H+ + 6e- 2Cr3+ + 7H2O, E = 1.33 V Fe3+(aq) + 3e- Fe E = -0.04 V Ni2+(aq) + 2e- Ni E = -0.25 V Ag+(aq) + e- Ag E = 0.80 V Au3+(aq) + 3e- Au E = 1.40 V Consider the given electrochemical reactions, The number of metal(s) which will be oxidized by Cr2O72-, in aqueous solution is .

Match List I with List II Choose the correct answer from the options given below:

1. A-III, B-I, C-IV, D-II
2. A-I, B-II, C-III, D-IV
3. A-IV, B-III, C-I, D-II
4. A-II, B-III, C-IV, D-I

Which out of the following is a correct equation to show change in molar conductivity with respect to concentration for a weak electrolyte, if the symbols carry their usual meaning :

1. m - m + AC 12 = 0
2. m2C + Ka m 2 - Ka m m = 0
3. m - m - AC 12 = 0
4. m2C - Ka m 2 + Ka m m = 0

The emf of cell Tl | Tl+ (0.001 M) | | Cu2+ (0.01 M) | Cu is 0.83 V at 298 K. It could be increased by :

1. increasing concentration of Tl+ ions
2. increasing concentration of Cu2+ ions
3. increasing concentration of both Tl+ and Cu2+ ions
4. decreasing concentration of both Tl+ and Cu2+ ions

The reaction; 12H2(g) + AgCl(s) H+(aq) + Cl-(aq) + Ag(s) occurs in which of the following galvanic cell :

1. Pt | H2(g) | HCl(soln.) | AgNO3(aq) | Ag
2. Ag | AgCl(s) | KCl(soln.) | AgNO3(aq.) | Ag
3. Pt | H2(g) | KCl(soln.) | AgCl(s) | Ag
4. Pt | H2(g) | HCl(soln.) | AgCl(s) | Ag

A conductivity cell with two electrodes (dark side) are half filled with infinitely dilute aqueous solution of a weak electrolyte. If volume is doubled by adding more water at constant temperature, the molar conductivity of the cell will - [figure]

1. depend upon type of electrolyte
2. increase sharply
3. decrease sharply
4. remain same or can not be measured accurately

How can an electrochemical cell be converted into an electrolytic cell ?

1. Applying an external opposite potential greater than E0cell
2. Exchanging the electrodes at anode and cathode.
3. Applying an external opposite potential lower than E0cell
4. Reversing the flow of ions in salt bridge.

Molar ionic conductivities of divalent cation and anion are 57 S cm2 mol-1 and 73 S cm2 mol-1 respectively. The molar conductivity of solution of an electrolyte with the above cation and anion will be:

1. 187 S cm2 mol-1
2. 260 S cm2 mol-1
3. 65 S cm2 mol-1
4. 130 S cm2 mol-1

The reaction at cathode in the cells commonly used in clocks involves.

1. oxidation of Mn from +2 to +7
2. reduction of Mn from +4 to +3
3. oxidation of Mn from +3 to +4
4. reduction of Mn from +7 to +2

The quantity of silver deposited when one coulomb charge is passed through AgNO3 solution :

1. 0.1 g atom of silver
2. 1 chemical equivalent of silver
3. 1 g of silver
4. 1 electrochemical equivalent of silver

For the electrochemical cell M | M2+ || X | X2- If E0(M2+/M) = 0.46 V and E0(X/X2-) = 0.34 V. Which of the following is correct?

1. Ecell = 0.80 V
2. M + X M2+ + X2- is a spontaneous reaction
3. Ecell = -0.80 V
4. M2+ + X2- M + X is a spontaneous reaction

One of the commonly used electrode is calomel electrode. Under which of the following categories, calomel electrode comes?

1. Metal ion - Metal electrodes
2. Oxidation - Reduction electrodes
3. Metal - Insoluble Salt - Anion electrodes
4. Gas - Ion electrodes

What pressure (bar) of H2 would be required to make emf of hydrogen electrode zero in pure water at 25 ?

1. 0.5
2. 10-14
3. 1
4. 10-7

Fuel cell, using hydrogen and oxygen as fuels, Choose the correct answer from the options given below:

1. A, D, E only
2. A, B, C only
3. A, B, D only
4. A, B, D, E only